Load applicator and power storage apparatus

ABSTRACT

A load applicator includes an elastic mechanism, a first member configured to move in accordance with contraction of power storage cells, a second member provided on a side opposite to the first member across the elastic mechanism, and a switching device. The elastic mechanism has a first form in which a first restraint load is applied to the power storage module when the power storage module expands by a first dimension, and a second form in which a second restraint load larger than the first restraint load is applied to the power storage module when the power storage module expands by the first dimension. The switching device performs an operation to switch from the first form to the second form in a case where a restraint load smaller than the first restraint load is applied to the power storage module when the power storage module expands by the first dimension.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2021-010990 filed on Jan. 27, 2021, incorporated herein by reference inits entirety.

BACKGROUND 1. Technical Field

This disclosure relates to a load applicator and a power storageapparatus.

2. Description of Related Art

As described in Japanese Unexamined Patent Application Publication No.2014-175078 (JP 2014-175078 A) or Japanese Unexamined Patent ApplicationPublication No. 2003-036830 (JP 2003-036830 A), a power storage moduleis configured such that a plurality of power storage cells is connectedin series or in parallel to each other in an integrated manner. A powerstorage apparatus includes a power storage module and a load applicatorconfigured to apply a restraint load to the power storage module. Theload applicator is configured to apply an appropriate restraint load fora long period, so that it is possible to achieve performance stable fora long period in the power storage apparatus.

SUMMARY

When the load applicator is used for a long period, there is such apossibility that the load applicator cannot apply a necessary andsufficient load to the power storage module due to deterioration byaging, or the like, for example. For example, in a case where the powerstorage cells constituting the power storage module contract in onedirection, a load to be applied from the load applicator to the powerstorage module in the one direction may become insufficient.

As measures to such a case, it is conceivable that the load applicatoris configured in advance to apply an excess load to prepare for anamount to become insufficient. However, this can separately cause such aconcern that an excessive load may be applied at an initial stage of useor this can separately cause such a necessity that the power storagemodule should have a strong structure sufficient to tolerate a largeload.

An object of this disclosure is to provide a load applicator having aconfiguration that can apply an appropriate load to a target object fora long period as compared to the related art, and a power storageapparatus including such a load applicator.

A load applicator of this disclosure is a load applicator for applying arestrain load to a power storage module including a plurality of powerstorage cells. The load applicator includes an elastic mechanism, afirst member, a second member, and a switching device. The first memberis placed between the elastic mechanism and the power storage module inone direction. The first member is configured to move along the onedirection along with contraction of the power storage cells. The secondmember is provided on a side in the one direction, the side beingopposite to a side where the first member is placed, across the elasticmechanism. The elastic mechanism contracts so as to correspond to adistance between the first member and the second member in the onedirection. The elastic mechanism applies a restraint load to the powerstorage module via the first member in accordance with a contractionamount of the elastic mechanism. The elastic mechanism has a first formin which a first restraint load is applied to the power storage modulewhen the power storage module expands by a first dimension, and a secondform in which a second restraint load larger than the first restraintload is applied to the power storage module when the power storagemodule expands by the first dimension. The switching device isconfigured to perform an operation to switch from the first form to thesecond form in a case where a restraint load smaller than the firstrestraint load is applied to the power storage module when the powerstorage module expands by the first dimension.

In the load applicator, the one direction may be a direction where thepower storage cells are stacked.

In the load applicator, an elastic modulus of the elastic mechanism in acase where the second form is formed may be larger than an elasticmodulus of the elastic mechanism in a case where the first form isformed.

In the load applicator, the elastic mechanism forming the first form mayinclude a predetermined number of elastic bodies configured to apply arestraint load to the power storage module. The elastic mechanismforming the second form may include elastic bodies the number of whichis greater than the predetermined number, the elastic bodies beingconfigured to apply a restraint load to the power storage module.

In the load applicator, the first member may include a first part and asecond part having a thickness thicker than a thickness of the firstpart in the one direction. In a state where the elastic mechanism formsthe first form, the elastic mechanism may apply a restraint load to thepower storage module via the first part of the first member. In a statewhere the elastic mechanism forms the second form, the elastic mechanismmay apply a restraint load to the power storage module via the secondpart of the first member.

A power storage apparatus according to this disclosure includes a powerstorage module and the load applicator described above. The powerstorage module includes a plurality of power storage cells. In a statewhere respective SOC values of the power storage cells constituting thepower storage module are set to values out of a predetermined range, theswitching device performs switching from the first form to the secondform.

With the above configuration, it is possible to achieve a loadapplicator having a configuration that can apply an appropriate load toa target object for a long period as compared to the related art, and apower storage apparatus including such a load applicator.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like signs denote likeelements, and wherein:

FIG. 1 is a plan view illustrating a load applicator and a power storageapparatus according to Embodiment 1 and illustrates a state where anelastic mechanism of the load applicator forms a first form;

FIG. 2 is a plan view illustrating the load applicator and the powerstorage apparatus according to Embodiment 1 and illustrates a statewhere the elastic mechanism of the load applicator forms a second form;

FIG. 3 is a plan view illustrating the load applicator and the powerstorage apparatus according to Embodiment 1 and illustrates a statewhere a switching device of the load applicator performs a switchingoperation to switch the elastic mechanism from the first form to thesecond form; FIG. 4 is a plan view illustrating the load applicator andthe power storage apparatus according to Embodiment 1 and illustrates astate where a restraint load to be applied to a power storage module bythe load applicator becomes smaller than that in the case illustrated inFIG. 1;

FIG. 5 is a plan view illustrating the load applicator and the powerstorage apparatus according to Embodiment 1 and illustrates a statewhere the restraint load to be applied to the power storage module bythe load applicator becomes larger than that in the case illustrated inFIG. 4 due to completion of the operation to switch from the first formto the second form;

FIG. 6 is a plan view illustrating the load applicator and the powerstorage apparatus according to a modification of Embodiment 1;

FIG. 7 is a plan view illustrating a load applicator and a power storageapparatus according to Embodiment 2 and illustrates a state where theelastic mechanism of the load applicator forms a first form;

FIG. 8 is a plan view illustrating the load applicator and the powerstorage apparatus according to Embodiment 2 and illustrates a statewhere the elastic mechanism of the load applicator forms a second form;and

FIG. 9 is a plan view illustrating the load applicator and the powerstorage apparatus according to Embodiment 2 and illustrates a statewhere the switching device of the load applicator performs an operationto switch the elastic mechanism from the first form to the second form.

DETAILED DESCRIPTION OF EMBODIMENTS

The following describes embodiments of the present disclosure. In a casewhere a number, an amount, and the like are mentioned in the embodimentsdescribed below, the scope of this disclosure is not necessarily limitedto the number, the amount, and the like, unless otherwise specified.Each constituent is not necessarily essential for this disclosure unlessotherwise specified. The same reference numeral is assigned to the samecomponent and its equivalent component, and a redundant description maynot be repeated.

The absolute values of the dimensions (e.g., L0, L1, D1 illustrated inFIG. 1) of constituents illustrated in the drawings and relative ratiostherebetween may not be necessarily illustrated faithfully as theiractual values, and the dimensions may be exaggerated for convenience ofthe description.

Embodiment 1 Power Storage Apparatus 100

FIG. 1 is a plan view illustrating a load applicator 60 and a powerstorage apparatus 100 according to Embodiment 1. The power storageapparatus 100 includes a power storage module 50, the load applicator60, an end plate 70, and restraining tools 91, 92. The power storagemodule 50 includes a plurality of power storage cells 5. An insulatingmember (not illustrated) is placed between two power storage cells 5adjacent to each other, so that the two power storage cells 5 adjacentto each other are electrically insulated from each other.

The load applicator 60 applies a restraint load to the power storagemodule 50 in collaboration with the end plate 70 and the restrainingtools 91, 92. More specifically, the load applicator 60 includes anelastic mechanism 30, a receiving member 10 (a first member), an endplate 20 (a second member), and a switching device 40.

The receiving member 10 is placed between the elastic mechanism 30 andthe power storage module 50 in one direction 80 and moves along the onedirection 80 along with contraction of one or more power storage cells5. The end plate 20 is provided on a side, in the one direction 80, thatis opposite to a side where the receiving member 10 is placed, acrossthe elastic mechanism 30. Here, the one direction 80 is a directionwhere the power storage cells 5 are stacked. The one direction 80 maynot be a direction parallel to the direction where the power storagecells 5 are stacked. The one direction 80 may be a directionintersecting with the direction where the power storage cells 5 arestacked.

The receiving member 10 includes a main body portion 11 and an expansionportion 12 projecting from the main body portion 11 toward the end plate20 side. An inclined surface 13 is formed on the expansion portion 12,and the inclined surface 13 is provided to face a position where arestriction member 36 (particularly, an inclined portion 36 t)(described later) is placed.

The load applicator 60 including the end plate 20 is placed on a firstside from the power storage module 50 in the one direction 80. The endplate 70 is placed on a second side from the power storage module 50 inthe one direction 80. The end plates 20, 70 have a plate shape and madeof metal, for example. First end parts of the restraining tools 91, 92are fixed to the end plate 20, and second end parts of the restrainingtools 91, 92 are fixed to the end plate 70. The end plate 20 isconnected to the end plate 70 via the restraining tools 91, 92.

The elastic mechanism 30 includes elastic bodies 31, 32, 33 and therestriction member 36. The elastic bodies 31, 32, 33 and the restrictionmember 36 are provided between the receiving member 10 and the end plate20 in the one direction 80. The elastic bodies 31, 32, 33 may be made ofelastically deformable resin, for example, and may be made of springshaving various shapes such as a plate shape, a dish shape, and a helicalshape. The restriction member 36 is placed adjacent to the elastic body32, and the inclined portion 36 t is provided in a distal end of therestriction member 36. The elastic mechanism 30 has a first form S1illustrated in FIG. 1 and a second form S2 illustrated in FIG. 2.

First Form S1 and Second Form S2

In a state where the elastic mechanism 30 forms the first form S1 (FIG.1), the elastic bodies 31, 33 of the elastic mechanism 30 contract so asto correspond to a distance D1 between the receiving member 10 and theend plate 20 in the one direction 80. In the state where the elasticmechanism 30 forms the first form S1, the elastic mechanism 30 (theelastic bodies 31, 33) applies a restraint load (arrows 71, 73) to thepower storage module 50 via the receiving member 10 in accordance withthe contraction amount (stroke amount) of the elastic mechanism 30, morespecifically, respective contraction amounts of the elastic bodies 31,33.

In the state where the elastic mechanism 30 forms the first form S1(FIG. 1), the inclined portion 36 t of the restriction member 36 islocked engagingly by a distal end of the elastic body 32, and theelastic body 32 is maintained by the restriction member 36 to be shorterthan its own natural length (the length in an unloaded condition). Theelastic body 32 forms a compressed state (a state where the elastic body32 has an internal stress (an arrow 72) in the one direction 80). Thedistal end of the elastic body 32 is distanced from the expansionportion 12 of the receiving member 10, so that the internal stress (thearrow 72) does not act on the receiving member 10.

In a state where the elastic mechanism 30 forms the second form S2 (FIG.2), the elastic body 32 is released from the engagingly locked statewith the restriction member 36, and the elastic bodies 31, 32, 33 allmake contact with the receiving member 10 and the end plate 20. Theelastic bodies 31, 32, 33 of the elastic mechanism 30 contract so as tocorrespond to a distance D2 between the receiving member 10 and the endplate 20 in the one direction 80.

That is, the elastic modulus of the elastic mechanism 30 in a case wherethe second form S2 is formed is larger than the elastic modulus of theelastic mechanism 30 in a case where the first form S1 is formed. In thestate where the elastic mechanism 30 forms the second form S2, theelastic mechanism 30 (the elastic bodies 31, 32, 33) applies a restraintload (the arrows 71, 72, 73) to the power storage module 50 via thereceiving member 10 in accordance with the contraction amount of theelastic mechanism 30, more specifically, respective contraction amountsof the elastic bodies 31, 32, 33.

FIG. 1 illustrates the state where the elastic mechanism 30 forms thefirst form S1. FIG. 2 illustrates the state where the elastic mechanism30 forms the second form S2. The switching device 40 is configured toperform switching from the first form S1 to the second form S2. Herein,the switching device 40 includes a controlling portion, a chargingcircuit, and so on (not illustrated), and the switching device 40 isconnected to the power storage module 50. Charging and discharging ofthe power storage cells 5 constituting the power storage module 50 canbe performed by the switching device 40, and the state of charge (SOC)can be set to any value by the switching device 40.

Assume a case where, in a state where the SOC is set to a predeterminedvalue, the power storage module 50 has a predetermined reference lengthL0 in the one direction 80. In the first form S1 (FIG. 1), in a casewhere the power storage module 50 expands by a first dimension L1 fromthe reference length L0, a first restraint load (the arrows 71, 73) isapplied to the power storage module 50 by the elastic mechanism 30 ofthe load applicator 60.

In the second form S2 (FIG. 2), in a case where the power storage module50 expands by the first dimension L1 from the reference length L0, asecond restraint load (the arrows 71, 72, 73) is applied to the powerstorage module 50 by the elastic mechanism 30 of the load applicator 60.The second restraint load (the arrows 71, 72, 73) is a value larger thanthe first restraint load (the arrows 71, 73).

FIG. 3 illustrates a state where the switching device 40 of the loadapplicator 60 performs a switching operation to switch the elasticmechanism 30 from the first form S1 to the second form S2. For example,in a state where the switching device 40 sets respective SOC values ofthe power storage cells 5 constituting the power storage module 50 tovalues out of a predetermined range, the switching device 40 performsswitching from the first form S1 to the second form S2.

In the configuration illustrated in FIG. 3, the SOC is to a value largerthan a normal usage range, so that the power storage module 50 expandsby a second dimension L2 from the reference length L0. The seconddimension L2 is a value larger than the first dimension L1. Due to theexpansion of the power storage module 50, the receiving member 10 movesin the one direction 80 more largely than in the cases illustrated inFIGS. 1, 2.

When the inclined surface 13 of the expansion portion 12 makes contactwith the inclined portion 36 t of the restriction member 36, theengagingly locked state of the restriction member 36 (the inclinedportion 36 t) with the elastic body 32 is released, so that the elasticbody 32 extends. Hereby, the switching from the first form S1 to thesecond form S2 by the switching device 40 is completed. The restrictionmember 36 should keep connected to the end plate 20 so that foreignmatter or abnormal noise does not occur.

Operations and Effects

As described at the beginning, when the power storage apparatus 100 orthe load applicator 60 is used for a long period, there is such apossibility that the load applicator 60 cannot apply a necessary andsufficient load to the power storage module 50 due to deterioration byaging, or the like, for example. For example, the lengths of the elasticbodies 31, 33 may become shorter than their initial states under theinfluence of creep deformation. Alternatively, the elastic moduli(Young's moduli) of the elastic bodies 31, 33 may become smaller thantheir initial states under the influence of creep deformation.

In FIG. 4, for convenience of the description, the phenomenon asdescribed above is expressed as the receiving member 10 becoming thin.As illustrated in FIG. 4, in a case where the phenomenon occurs, whenthe power storage module 50 expands by the first dimension L1 from thereference length L0, a restraint load smaller than the first restraintload (corresponding to the arrows 71, 73 in FIG. 1) is applied to thepower storage module 50. In such a case, the switching device 40 isconfigured to perform an operation to switch from the first form S1 tothe second form S2 by performing the operation described with referenceto FIG. 3.

FIG. 5 illustrates a state where the restraint load to be applied to thepower storage module 50 by the load applicator 60 becomes larger thanthat in the case illustrated in FIG. 4 due to completion of theoperation to switch from the first form S1 to the second form S2. Thisstate is a state different from the first form S1 and the second form S2to be provided at the time of starting the use of the load applicator60. Since this state is formed, even in a case where the power storagecells 5 constituting the power storage module 50 contract in the onedirection 80, it is possible to effectively restrain insufficiency inthe load to be applied from the load applicator 60 to the power storagemodule 50 in the one direction 80, just by an increase in the load bythe elastic body 32.

Accordingly, with the above configuration, it is possible to achieve theload applicator 60 having a configuration that can apply an appropriateload to a target object for a long period as compared to the relatedart, and the power storage apparatus 100 including such a loadapplicator 60. For example, in a case where the power storage apparatus100 (e.g., a fully solid battery) having a high capacity is formed, anelastic body such as resin can be employed or effectively utilized as amaterial having a higher expansion coefficient. Even in such a case, byemploying the technical idea described in the present embodiment, it ispossible to take measures to creep deformation of the elastic body,thereby making it possible to achieve a longer operating life of thepower storage apparatus 100 as a product.

In a case where the power storage apparatus 100 is used to be providedin a vehicle, the power storage apparatus 100 can be placed at aposition where its maintenance is hard to be performed in general. Evenin such a case, only by performing an SOC control by the switchingdevice 40, e.g., without a maintenance operator physically accessing theload applicator 60, it is possible to perform the operation to switchfrom the first form S1 to the second form S2.

The degree of creep of the elastic body can be predicted to some extentbased on physical properties of the elastic body or the specificationrelated to the load applicator 60. The switching operation is performedby the switching device 40 at a timing when the restrain load maydecrease on design, and at this time, the switching operation isperformed under a cell chargeable environment.

For example, a predetermined threshold may be set based on values ofresistance values obtainable during charging and discharging, theintegrated number of times of charging and discharging, an integratedtime of charging and discharging, an operating temperature, anintegrated capacity for charging and discharging, a travel distance, orthe like. The arrival of the threshold may be notified (a state where anoperator can recognize the arrival of the threshold may be formed), orthe switching operation may be automatically performed by the switchingdevice 40 based on the arrival of the threshold.

In the load applicator 60, the number of elastic bodies acting on thereceiving member 10 increases along with changing from the first form S1to the second form S2. That is, the elastic mechanism 30 forming thefirst form S1 includes a predetermined number of elastic bodies 31, 33(herein, two elastic bodies 31, 33) configured to apply a restraint loadto the power storage module 50. The elastic mechanism 30 forming thesecond form S2 includes three elastic bodies 31, 32, 33 the number ofwhich is greater than the predetermined number (two), the elastic bodiesbeing configured to apply a restraint load to the power storage module50. Since the load applicator 60 has this configuration, it is possibleto perform the operation to switch from the first form S1 to the secondform S2 by an easy operation illustrated in FIG. 3.

Modification of Embodiment 1

FIG. 6 is a plan view illustrating the load applicator 60 and the powerstorage apparatus 100 according to a modification of Embodiment 1. InEmbodiment 1 described above, by performing the operation to switch fromthe first form S1 to the second form S2, one elastic body 32 is added totwo elastic bodies 31, 33 used to apply a restraint load to thereceiving member 10.

As illustrated in FIG. 6, the load applicator 60 may be configured suchthat, by performing the operation to switch from the first form S1 tothe second form S2, two elastic bodies 31, 33 are added to one elasticbody 32 used to apply a restraint load to the receiving member 10. Thenumber of elastic bodies and the elastic modulus of the whole elasticmechanism 30 should be designed in consideration of a restraint load tobe applied to the power storage module 50.

Embodiment 2

With reference to FIGS. 7 to 9, the following describes a loadapplicator 61 and a power storage apparatus 101 according to Embodiment2. FIG. 7 is a plan view illustrating the load applicator 61 and thepower storage apparatus 101 and illustrates a state where the elasticmechanism 30 of the load applicator 61 forms the first form S1. FIG. 8illustrates a state where the elastic mechanism 30 of the loadapplicator 61 forms the second form S2.

In the load applicator 61, the elastic mechanism 30 includes thereceiving member 10, an elastic body 37, and a pedestal 38. The elasticbody 37 is placed on the end plate 20 via the pedestal 38. The elasticbody 37 is provided between the receiving member 10 (a movable block 14(described later)) and the pedestal 38 in the one direction 80. Thereceiving member 10 includes the main body portion 11, the movable block14, and a feed mechanism 16. An inclined surface 15 is formed on themain body portion 11, and the movable block 14 moves on the inclinedsurface 15.

The receiving member 10 includes a first part P1 (FIG. 7) and a secondpart P2 (FIG. 8). The second part P2 has a thickness thicker than thatof the first part P1 in the one direction 80, and the inclined surface15 is formed due to the presence of the first part

P1 and the second part P2. In the load applicator 61, the elasticmechanism 30 has the first form S1 illustrated in FIG. 7 and the secondform S2 illustrated in FIG. 8.

In a state where the elastic mechanism 30 forms the first form S1 (FIG.7), the elastic body 37 of the elastic mechanism 30 contracts so as tocorrespond to the distance D1 between the receiving member 10 (themovable block 14) and the end plate 20 in the one direction 80. In thestate where the elastic mechanism 30 forms the first form S1, theelastic mechanism 30 applies a restraint load (an arrow 74) to the powerstorage module 50 via the first part P1 of the main body portion 11 ofthe receiving member 10. In the state where the elastic mechanism 30forms the first form S1, the elastic mechanism 30 (the elastic body 37)applies a restraint load (the arrow 74) to the power storage module 50via the receiving member 10 in accordance with the contraction amount ofthe elastic mechanism 30, more specifically, the contraction amount ofthe elastic body 37.

In a state where the elastic mechanism 30 forms the second form S2 (FIG.8), the elastic body 37 of the elastic mechanism 30 contracts so as tocorrespond to the distance D2 between the receiving member 10 (themovable block 14) and the end plate 20 in the one direction 80. In thestate where the elastic mechanism 30 forms the second form S2, theelastic mechanism 30 applies a restraint load (an arrow 75) to the powerstorage module 50 via the second part P2 of the main body portion 11 ofthe receiving member 10. In the state where the elastic mechanism 30forms the second form S2, the elastic mechanism 30 (the elastic body 37)applies a restraint load (the arrow 75) to the power storage module 50via the receiving member 10 in accordance with the contraction amount ofthe elastic mechanism 30, more specifically, the contraction amount ofthe elastic body 37.

The second part P2 has a thickness thicker than that of the first partP1 in the one direction 80. Accordingly, as the whole receiving member10, a thickness W2 of the receiving member 10 at the time when thesecond form S2 is formed is larger than a thickness W1 of the receivingmember 10 at the time when the first form S1 is formed.

Assume a case where, in a state where the SOC is set to a predeterminedvalue, the power storage module 50 has the predetermined referencelength L0 in the one direction 80. In the first form S1 (FIG. 7), in acase where the power storage module 50 expands by the first dimension L1from the reference length L0, a first restraint load (the arrow 74) isapplied to the power storage module 50 by the elastic mechanism 30 ofthe load applicator 61.

In the second form S2 (FIG. 8), in a case where the power storage module50 expands by the first dimension L1 from the reference length L0, asecond restraint load (the arrow 75) is applied to the power storagemodule 50 by the elastic mechanism 30 of the load applicator 61. Thesecond restraint load (the arrow 75) is a value larger than the firstrestraint load (the arrow 74).

FIG. 9 illustrates a state where the switching device 40 of the loadapplicator 61 performs a switching operation to switch the elasticmechanism 30 from the first form S1 to the second form S2. For example,in a state where the switching device 40 sets respective SOC values ofthe power storage cells 5 constituting the power storage module 50 tovalues out of a predetermined range, the switching device 40 performsswitching from the first form S1 to the second form S2.

In the configuration illustrated in FIG. 9, the SOC is set to a valuesmaller than the normal usage range, so that the power storage module 50expands by the second dimension L2 from the reference length L0. Thesecond dimension L2 is a value smaller than the first dimension L1. Dueto the expansion of the power storage module 50, the receiving member 10moves in the one direction 80 by an amount smaller than that in thecases illustrated in FIGS. 7, 8.

While such a state illustrated in FIG. 9 is being formed, or when thestate illustrated in FIG. 9 has been formed, the feed mechanism 16operates such that the position of the movable block 14 is changed fromthe first part P1 to the second part P2. The feed mechanism 16 may beadjusted such that a load is always applied to the feed mechanism 16 byan elastic body such as a spring, and when a frictional force betweenthe movable block 14 and the inclined surface 15 decreases, the feedmechanism 16 is pushed from the first part P1 side toward the secondpart P2 side. Hereby, the switching from the first form S1 to the secondform S2 by the switching device 40 is completed.

As described at the beginning, when the power storage apparatus 101 orthe load applicator 61 is used for a long period, there is such apossibility that the load applicator 61 cannot apply a necessary andsufficient load to the power storage module 50 due to deterioration byaging, or the like, for example. For example, the length of the elasticbody 37 may become shorter than its initial state under the influence ofcreep deformation. Alternatively, the elastic modulus (Young's modulus)of the elastic body 37 may become smaller than its initial state underthe influence of creep deformation.

In a case where such a phenomenon occurs, when the power storage module50 expands by the first dimension L1 from the reference length L0, arestraint load smaller than the first restraint load (corresponding tothe arrow 74 in FIG. 7) is applied to the power storage module 50. Insuch a case, the switching device 40 is configured to perform anoperation to switch from the first form S1 to the second form S2 byperforming the operation described with reference to FIG. 9.

When the operation to switch from the first form S1 to the second formS2 is completed, the restraint load to be applied to the power storagemodule 50 by the load applicator 61 increases. This state is a statedifferent from the first form S1 and the second form S2 to be providedat the time of starting the use of the load applicator 61. Since thisstate is formed, even in a case where the power storage cells 5constituting the power storage module 50 contract in the one direction80, it is possible to effectively restrain insufficiency in the load tobe applied from the load applicator 61 to the power storage module 50 inthe one direction 80, just by an increase in the load by the elasticbody 37.

The embodiments have been described above, but the embodiments describedherein are just examples in all respects and are not limitative. Thescope of this disclosure is shown by Claims and is intended to includeall modifications made within the meaning and scope equivalent toClaims.

What is claimed is:
 1. A load applicator for applying a restrain load toa power storage module including a plurality of power storage cells, theload applicator comprising: an elastic mechanism; a first member placedbetween the elastic mechanism and the power storage module in onedirection, the first member being configured to move along the onedirection along with contraction of the power storage cells; a secondmember provided on a side in the one direction, the side being oppositeto a side where the first member is placed, across the elasticmechanism; and a switching device, wherein: the elastic mechanismcontracts so as to correspond to a distance between the first member andthe second member in the one direction; the elastic mechanism applies arestraint load to the power storage module via the first member inaccordance with a contraction amount of the elastic mechanism; theelastic mechanism has a first form in which a first restraint load isapplied to the power storage module when the power storage moduleexpands by a first dimension, and a second form in which a secondrestraint load larger than the first restraint load is applied to thepower storage module when the power storage module expands by the firstdimension; and the switching device is configured to perform anoperation to switch from the first form to the second form in a casewhere a restraint load smaller than the first restraint load is appliedto the power storage module when the power storage module expands by thefirst dimension.
 2. The load applicator according to claim 1, whereinthe one direction is a direction where the power storage cells arestacked.
 3. The load applicator according to claim 1, wherein an elasticmodulus of the elastic mechanism in a case where the second form isformed is larger than an elastic modulus of the elastic mechanism in acase where the first form is formed.
 4. The load applicator according toclaim 3, wherein: the elastic mechanism forming the first form includesa predetermined number of elastic bodies configured to apply a restraintload to the power storage module; and the elastic mechanism forming thesecond form includes elastic bodies the number of which is greater thanthe predetermined number, the elastic bodies being configured to apply arestraint load to the power storage module.
 5. The load applicatoraccording to claim 1, wherein: the first member includes a first partand a second part having a thickness thicker than a thickness of thefirst part in the one direction; in a state where the elastic mechanismforms the first form, the elastic mechanism applies a restraint load tothe power storage module via the first part of the first member; and ina state where the elastic mechanism forms the second form, the elasticmechanism applies a restraint load to the power storage module via thesecond part of the first member.
 6. A power storage apparatuscomprising: a power storage module including a plurality of powerstorage cells; and the load applicator according to claim 1, wherein, ina state where respective SOC values of the power storage cellsconstituting the power storage module are set to values out of apredetermined range, the switching device performs switching from thefirst form to the second form.